1. Field of the Invention
This invention relates to devices for processing audio signals, and in particular to a digital microphone device.
2. Description of the Related Art
In recent years, the processing of audio signals has had considerable improvement. More specifically, the ability to integrate digital functions by VLSI-type technologies has made it possible to translate many analog functions into a digital format. It is currently possible to reproduce in a digital format effects that, in the past, could only be achieved in an analog format as equalizations which include filtering in general, surround effects, reverberations, and echoes. These effects have a better quality than in the past, when obtained in a digital format.
In addition, new and more advanced sub-micrometer manufacturing processes have resulted in smaller and more powerful digital integrated circuits which have a low cost. Consequently, conversion devices to convert analog signals to digital signals and vice versa, have obtained a great importance.
The trend toward a digital domain in the processing of audio signals is so marked that even signal sources, understood as reproduction devices, are now implemented join a digital format. Consequently, in systems for transmitting audio signals, microphone devices will soon be the only devices to be performed in an analog format.
Generally, the analog microphone devices include a transducer circuit to produce a voltage analog signal which is proportional to an audio signal generated by a sound source. In some microphone devices, this voltage analog signal is amplified before being transmitted over a cable or broadcast. In the case in which the voltage analog signal is broadcast, e.g. in cordless applications, it would have to be frequency-modulated before its transmission using carrier frequencies in the 170 MHz range.
The analog microphone devices, while being advantageous in many ways, still have some drawbacks such as coupling noise due to electromagnetic waves that surround the devices, attenuations, and filtering due to the transmitting means. Generally, these drawbacks decrease the quality of the transmitted signal.